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SingleFilePageSwapperFactory.java
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SingleFilePageSwapperFactory.java
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/*
* Copyright (c) 2002-2017 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.neo4j.io.pagecache.impl;
import java.io.File;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.CopyOption;
import java.nio.file.NoSuchFileException;
import java.util.List;
import java.util.stream.Stream;
import org.neo4j.graphdb.config.Configuration;
import org.neo4j.io.fs.FileSystemAbstraction;
import org.neo4j.io.pagecache.FileHandle;
import org.neo4j.io.pagecache.PageEvictionCallback;
import org.neo4j.io.pagecache.PageSwapper;
import org.neo4j.io.pagecache.PageSwapperFactory;
import static java.util.stream.Collectors.toList;
/**
* A factory for SingleFilePageSwapper instances.
*
* @see org.neo4j.io.pagecache.impl.SingleFilePageSwapper
*/
public class SingleFilePageSwapperFactory implements PageSwapperFactory
{
private FileSystemAbstraction fs;
@Override
public void open( FileSystemAbstraction fs, Configuration config )
{
this.fs = fs;
}
@Override
public PageSwapper createPageSwapper(
File file,
int filePageSize,
PageEvictionCallback onEviction,
boolean createIfNotExist ) throws IOException
{
if ( !fs.fileExists( file ) )
{
if ( createIfNotExist )
{
fs.create( file ).close();
}
else
{
throw new NoSuchFileException( file.getPath(), null, "Cannot map non-existing file" );
}
}
return new SingleFilePageSwapper( file, fs, filePageSize, onEviction );
}
@Override
public void syncDevice()
{
// Nothing do to, since we `fsync` files individually in `force()`.
}
@Override
public Stream<FileHandle> streamFilesRecursive( File directory ) throws IOException
{
return streamFilesRecursive( directory.getCanonicalFile(), fs );
}
@Override
public void close()
{
// We have nothing to close
}
/**
* Static implementation of {@link SingleFilePageSwapperFactory#streamFilesRecursive(File)} that does not require
* any external state, other than what is presented through the given {@link FileSystemAbstraction}.
*
* This method is an implementation detail of {@link PageSwapperFactory page swapper factories}, and it is made
* available here so that other {@link PageSwapperFactory} implementations can use it as the basis of their own
* implementations. In other words, so that other {@link PageSwapperFactory} implementations can implement
* {@link PageSwapperFactory#streamFilesRecursive(File)} by augmenting this stream.
* @param directory The base directory.
* @param fs The {@link FileSystemAbstraction} to use for manipulating files.
* @return A {@link Stream} of {@link FileHandle}s, as per the {@link PageSwapperFactory#streamFilesRecursive(File)}
* specification.
* @throws IOException If anything goes wrong, like {@link PageSwapperFactory#streamFilesRecursive(File)} describes.
*/
public static Stream<FileHandle> streamFilesRecursive( File directory, FileSystemAbstraction fs ) throws IOException
{
try
{
// We grab a snapshot of the file tree to avoid seeing the same file twice or more due to renames.
List<File> snapshot = streamFilesRecursiveInner( directory, fs ).collect( toList() );
return snapshot.stream().map( f -> new WrappingFileHandle( f, directory, fs ) );
}
catch ( UncheckedIOException e )
{
// We sneak checked IOExceptions through UncheckedIOExceptions due to our use of streams and lambdas.
throw e.getCause();
}
}
private static Stream<File> streamFilesRecursiveInner( File directory, FileSystemAbstraction fs )
{
File[] files = fs.listFiles( directory );
if ( files == null )
{
if ( !fs.fileExists( directory ) )
{
throw new UncheckedIOException( new NoSuchFileException( directory.getPath() ) );
}
return Stream.of( directory );
}
return Stream.of( files )
.flatMap( f -> fs.isDirectory( f ) ? streamFilesRecursiveInner( f, fs ) : Stream.of( f ) );
}
@Override
public String implementationName()
{
return "single";
}
@Override
public int getCachePageSizeHint()
{
return 8192;
}
@Override
public boolean isCachePageSizeHintStrict()
{
return false;
}
@Override
public long getRequiredBufferAlignment()
{
return 1;
}
private static class WrappingFileHandle implements FileHandle
{
private final File file;
private final File baseDirectory;
private final FileSystemAbstraction fs;
WrappingFileHandle( File file, File baseDirectory, FileSystemAbstraction fs )
{
this.file = file;
this.baseDirectory = baseDirectory;
this.fs = fs;
}
@Override
public File getFile()
{
return file;
}
@Override
public File getRelativeFile()
{
int baseLength = baseDirectory.getPath().length();
if ( baseDirectory.getParent() != null )
{
baseLength++;
}
return new File( file.getPath().substring( baseLength ) );
}
@Override
public void rename( File to, CopyOption... options ) throws IOException
{
File parentFile = file.getParentFile();
fs.mkdirs( to.getParentFile() );
fs.renameFile( file, to, options );
removeEmptyParent( parentFile );
}
private void removeEmptyParent( File parentFile )
{
// delete up to and including the base directory, but not above.
// Note that this may be 'null' if 'baseDirectory' is the top directory.
// Fortunately, 'File.equals(other)' handles 'null' and returns 'false' when 'other' is 'null'.
File end = baseDirectory.getParentFile();
while ( parentFile != null && !parentFile.equals( end ) )
{
File[] files = fs.listFiles( parentFile );
if ( files == null || files.length > 0 )
{
return;
}
fs.deleteFile( parentFile );
parentFile = parentFile.getParentFile();
}
}
@Override
public void delete() throws IOException
{
File parentFile = file.getParentFile();
fs.deleteFileOrThrow( file );
removeEmptyParent( parentFile );
}
}
}